In the ad, which went up on air Wednesday and is not yet available on YouTube, Leach says, “If you want Republican politics, vote for one of them.”

On Boyle, whom Democratic operatives say is a formidable opponent due to his strong union and Philadelphia political machine support, Leach says, “Brendan Boyle opposed a woman’s right to chose. I’m strongly pro-choice.”

On Margolies, whom many Democratic operatives have seen as the front-runner in the race, Leach says, “Marjorie Margolies would cut Social Security benefits. I say the wealthiest should pay their fair share to protect social security.”

On Arkoosh, one of the strongest fundraisers in the contest, Leach says, “Val Arkoosh is massively funded by groups that fought Obamacare.”

Such a negative ad is a risky strategy in a crowded primary. Democratic operatives in Philadelphia said the tone is part of Leach’s boisterous personality — Leach describes himself as a “liberal lion” and has the endorsement of a similarly outspoken progressive in Rep. Alan Grayson, D-Fla.

The May 20 Democratic primary is likely to determine the next member of Congress from this district, which voted for President Barack Obama with 66 percent in 2012. Democratic Rep. Allyson Y. Schwartz is vacating the seat to run for governor.

With two weeks to go, Democratic strategists say the race is close.

The general-election race is rated Safe Democratic by Rothenberg Political Report/Roll Call.